Pressure controlled electric switch



Nov. 17, 1942. s. R. DU BRIE PRESSURE CONTROLLED ELECTRIC SWITCH 3Sheets-Sheet 1 4 mp 7 H L w 6 n 0 2 a W 8 J v E m b. a. II

Nov. 17, 1942. s. R. DU BRIE 2,302,534

PRESSURE CONTROLLED ELECTRIC SWITCH Filed Oct. 16, 1940 s Sheets-Sheet 2I 26- Jfwr/sw Z DUE/v:

INVENT OR.

Nov. 17, 1942. s. R. DU BRIE PRESSURE CONTROLLED ELECTRIC, SWITCH File dOct. 16, 1940 3 Sheets-Sheet 3 Patented Nov. 17, 1942 PRESSURECONTROLLED ELECTRIC SWITCH .Stanley R. Du Brie, Detroit, Mich., assignorto Pickering Products Corp, Detroit, Mich., a corporation of MichiganApplication October 16, 1940, Serial No. 361,360

' Claims.

This invention relates to pressure controlled electric switches for usein conjunction with electrically driven air compressors or the like.

The usual compressors of this character have a pump and storage tankwherein the pressure is required to be maintained between certain highand low. limits.

The object of my invention is to provide a new form ofswitchoperating toclose the electric circuit to the motor at certain low tank pressure andto break the circuit and cease operation of the pump at certain hightank pressure and includes a new and unique make and break mechanism forthe electric circuit. It also, preferably, includes a means forrelieving the compressor from pressure when the electric circuit isbroken thereby enabling the compressor to be started practically freefrom load.

The invention 'further seeks to provide certain new structural featuresincluding a unique form of make and break switch actuated by variationin tank pressure, all of which is hereinafter more fully described andclaimed.

The preferred form of construction of a pressure controlled switchapparatus is shown in the accompanying drawings in which Fig. 1 is aplan view of the switch mechanism, the casing being broken away to showparts thereof.

Fig. 2 is avertical section taken on line 22 of Fig. 1.

Fig. 3 is a vertical section taken on line 3-3 of Fig. 1.

Fig. .4 is a vertical section taken'on line 4-4 of Fig. 1.

Fig. 5 is a perspective view ofan adjustable block for varying thepressure at which the apparatus will function to break the circuit.

Fig. 6 is a plan view showing the pivotal support for the breaker armtaken on the bracketed line 6 in Fig. 2.

Fig. 7 is a section showing the said pivoted support on line l-'! ofFig. 2 and of Fig. 6.

Fig. 8 is an elevation showing a typical installation of my improvedswitch as associated with an air compressor and storage tank.

My improved apparatus as hereinafter described is for use in themaintenance of an under pressure in storage tanks providing a source ofsupply for conduits leading to air controlled or operated apparatus, asfor instance hammers. and in which system it is desired to maintain thepressure between a minimum and maximum pressure.

The apparatus under control of the switch mechanism may be typically asshown in Fig. 8 in which there is a storage tank I, a compressor 2driven by a belt from the pulley of the electric motor 3. The compressorintake 4 is screened and the outlet 5 to the tank I has an enlargedchambered portion 6 from which a conduit I extends to a housing 8 whichalso has a conduit 9 discharging to atmosphere and the function of whichis hereinafter described. The motor is here shown as having a three wirecircuit indicated generally at l0 which leads into the casing ll of theswitch indicated at H in Fig. 1 and leads therefrom by the wires l2 tothe'motor, the casing having fittings I3 and I4 through which the wirespass into and from the casing.

Within the casing is the switch block l5 of insulating material havingparallel grooves in the upper face in which are secured the terminals l6and I! in the respective grooves for each of the three'wires. Thisarrangement will be clearly m'iderstood from Figs. 2 and 3 in which is acover [B'for these grooves. The terminals l6 and I! have horizontalportions shown in dotted lines in'Fig. 2 ,spaced'apart and engageable bythe contact l9 each carried by the upper end of the respective switchstem-20 which are vertically movable in the relationship of the partsshown to break the circuit when in the position shown in dotted lines inFig. 4-or closethe circuit by the respective springs 20a in the positionshown in full lines in said figure.

In'order to make or break the'three wire circuit here shown the threeswitch stems-must be simultaneously engaged to compress the springs 20aand break the circuit and to likewise simultaneously release the stem toclose the circuit and as heretofore stated it is desirable to' break thecircuit onattainment of predetermined pressure in thestorage tankandautomatically close the circuit when the pressure has decreased to apredetermined extent. It is also desirable that thesmake or break ofeach circuit be rapid: in order to reduceor prevent'arcing at theterminals. Furthermore it is desirable that the switch apparatusbeadjustable to make or break thecircuitiata lower or a higher'pressure asmay be'required depending upon the service demanded byithe air line 2|leading from the tank to the pressure operated apparatus.

For this purpose I provide a switch actuator shown in longitudinalsection in Fig. 4 which comprises a-plate 22 having an aperture toreceive a pin 23 supported by a plate 24 which inturn is secured toa'fiexible' diaphragm'25 within the chamber 26 connected by aconduit 21with the interior of the tank. The position of the diaphragm isdetermined by the pressure in the tank and this determines the positionof the plate 22 which may occupy the position shown in section in Fig. 2or may occupy the dotted line position shown in Fig. 2. This plate 22,as shown in plan view in Fig. 1, has a recess 23 opening centrallythrough one edge thereof and on opposite sides of the opening the plateis pressed downwardly by coiled springs 29 mounted on the bolts 30 andhaving a retaining cap 3 l The bolts are each threaded at the upper endto receive a nut 32 by which the tension of the spring 36 may be varied.The plate 22 at the end thereof opposite the spring restrained end ispivoted on a shaft 33 by the ears 34 on opposite sides of the casing asshown clearly in Fig. 3. The switch block I is supported in position inthe upper part of the casing by the sheet metal standards 35 on oppositesides thereof as will be understood from Figs. 2, 3 and 4. Each of thesestandards has an inturned portion 36 of V-form and the stem actuator 3?has legs 33 on each of its opposite sides which are notched to fit intothe V-form portion 36 which functions as a pivot for the stem actuator31.

This actuator shown in Fig. 3 is of sheet metal form and lies with thecrowned portion thereof beneath the switch stems and has a substantiallyvertical portion 39 at the end opposite the pivots to the lower end ofwhich is attached one end of the coiled spring 40, the opposite end ofwhich is secured to the lugs 4| of the adjusting block 42. The block 42has grooves 43 in its opposite side edges which engage the 0ppositeedges of the recess 28 in the plate 22 as clearly shown in Fig. 1. Theblock further has a central threaded aperture 44 to receive the screw 45which has a head 45 provided with flat sides which may engage the spring41 on the sliding block 42 which prevents accidental rotation of thescrew. By rotation of the screw the block is caused to be moved in onedirection or the other in the recess to increase or decrease the tensionof the spring 40. In the position of the parts shown in Fig. 4, the endof the spring attached to the block is above a horizontal lin extendingthrough the point of attachment of the spring with the down-turnedflange 39 of the switch actuator and normally tends to hold the actuatorin the position shown in section in Fig. 4. Under the said relationshipof parts the contact l9 carried by each of the stems 20 are maintainedin contact with the respective terminals [6 and H by the respectivesprings 20a.

In this position of the contact elements, the circuit to the motor isclosed thereby causing the compressor to be operated and to dischargeair under pressure to the tank I and as the conduit 21 is open to thetank, pressure will be produced in the chamber which exerts pressure onthe plate 22 tending to raise the same under restraint of the springs tothe position shown in dotted lines in Fig. 4. This raises the end of thespring attached to the sliding block and at a certain point above thehorizontal line passing through the point 40, the tension of the springwill cause the actuator to snap upwardly under tension of the spring totain degree the spring 30 tends to move the plate 22 downwardly from thedotted position to the full line position shown, permitting the circuitto again be closed by influence of the springs 20a causing engagement ofthe contact I9 with the terminals l6 and H.

Upon cessation of operation of the motor and consequently of thecompressor, the air pressure at the head of the pistons is approximatelyequal to the pressure in the tank and under such condition the motorwould be required to start the compressor under full load. To obviatesuch undesirable condition, I provide a means for relieving the pressurein the cylinder head and conduits 5, B and 7 between the check valve andthe compressor which check valve '50 is closed by pressure in the tankI.

The conduit 1 opens to a housing 8 which has a spring seated valve 5!provided with a stem 52 projecting from the lower side of the housingand a spring 53 tending to seat the valve. The housing also has aconduit 9 open to the chamber therein and discharging to atmosphere. Apivoted lever 54 is provided having an end extending into the casing andhas a down-turned end portion 55 extending over th upper surface of theactuator 31. When the actuator is in the position shown in full lines inFigs. 3 and 4, the valve is seated and when the actuator is moved to thedotted line position shown in Fig. 4 the lever 54 is raised to thedotted line position shown in Fig. 3 raising the valve 5| to the dottedline position thereby permitting escape of air from the compressorcylinder and pressure conduits 5, 5 and 7 thus relieving the cylinderfrom pressure and permitting the compressor to be started free fromexcess load.

It is to be understood that the invention is not limited to use in athree wire electric circuit as the device may be readily designed foruse with circuits involving one or more wires. A basic feature of theinvention is involved in the structure of the switch actuating mechanismwhich includes the switch actuator 31, the spring 40 and a means forvarying the tension of the spring and the arrangement of parts whereinvariation in pressure in the service line or storage tank varies theposition of the plate 22 and consequently the positioning of the springin such angular relation to the switch actuator as to move the same inone direction or the other in response to a high or a low pressurecondition in the tank or service line.

It is believed evident from the foregoing description that the variousfeatures and objects of the invention are attained by the describedrelationship of parts and that various changes may be made in thestructure and form of parts within the spirit and scope of the appendedclaims.

Having thus fully described my invention, its utility and mode ofoperation, what I claim and desire to secure by Letters Patent of theUnited States is:

l. A pressur actuated switch comprising a frame, a pair of contacts ofan electric circuit supported in insulated relation by the frame, amovable contact element associated with said pair of contacts to make orbreak the circuit, a spring tending to move said movable contact to makethe circuit, means for moving said movable contact to break the circuitcomprising a plate pivoted at one end to the frame, a spring at theopposite movable end of the plate for resisting turning of the plate inone direction on its pivot, pressure actuated means for turning theplate on its pivot against the tension of said spring means, a switchactuator comprising an L-shaped member pivotally supported at one end tothe frame in a plane vertically above the plane of the pivotal point ofsaid plate and with the opposite end normally in contact with the plate,an adjustable member at the end of the plate opposite the pivoted end, aspring having one end attached to the said adjustable member and theother end attached to the free end of the L-shaped member said point ofattachment of the spring to the adjustable member being in a planebetween the pivot point of the L shaped member and the pivot point ofthe plate, said adjustable member providing for variation in the tensionof the spring attached thereto, the arrangement providing that, onturning the plate on its pivot by said pressure actuated means againstthe tension of said spring at the movable end thereof, the actuatorspring is caused to turn the actuator on its pivot and move said movablecontact element to break the circuit.

2. A pressure actuated switch comprising a frame, a pair of contacts ofan electric circuit supported in insulated relation by the frame, amovable contact element associated with said pair of contacts to make orbreak the circuit, a spring tending to move said movable contact to makethe circuit, means for moving said movable contact to break the circuitcomprising a plate pivoted at one end to the frame, a spring at theopposite movable end of the plate for resisting turning of the plate inone direction on its pivot, pressure actuated means for turning theplate on its pivot against the tension of said spring means, a switchactuator comprising a member pivotally supported at one end to the frameand with the opposite end normally in contact with the plate, anadjustable member slidable in slots provided at the end of the plateopposite the pivoted end, means for varying the position of theadjustable member in the slot a spring having one end attached to thesaid adjustable member and the other end attached to the pivoted switchactuator, movement of said adjustable member in the slot varying thetension of the spring attached thereto, the arrangement providing that,on turning the plate on its pivot by said pressure actuated meansagainst the tension of said spring at the movable end of the plate, theactuator spiing is caused to turn the actuator on its pivot and movesaid movable contact element to break the circuit, and means for varyingthe tension of the plate spring to thereby determine the pressure atwhich the switch will function to break the circuit.

3. A pressure controlled switch for making or breaking an electriccircuit comprising a frame having contacts for the circuit, a movableswitch element for making or breaking the circuit, a spring for movingthe switch element to make the circuit, a switch actuator comprising anL-shaped plate pivoted at its long end to the frame for moving theswitch element to break the circuit, a coiled spring having one endconnected to the short free end of the L-shaped plate and the oppositeend supported at a point substantially equi-distantly between thehorizontal planes respectively occupied by the free end of the actuatorin the switch actuating and non-actuating positions, means for varyingthe tension of the coiled spring, and a pivoted spring-restrained plateengaged by the short free end of the L-shaped plate responsive topredetermined pressure to turn the L-shaped plate on its pivot toposition to permit the coiled spring to thereafter move the Lshapedplate to engage the switch element and break the circuit.

4. A pressure controlled electric switch comprising a frame, a pair ofcontacts of an electric circuit supported in insulated relation by theframe, a movable contact element for making and breaking the circuit, aspring tending to move the said movable contact element to make thecircuit, means for moving said movable contact to break the circuitcomprising a plate pivoted at one end to the frame, spring means at theopposite movable end of the pivoted plate for resisting turning of theplate in one direction on its pivot, pressure actuated means for turningthe plate on its pivot against the tension of said spring means, aswitch actuator comprising an L-shaped plate pivotally supported at oneend by the frame at a point spaced from the movable end of the firstnamed pivoted plate, and with the opposite end engaging the first namedpivoted plate adjacent its pivot point, a spring attached at one end tothe L-shaped plate adjacent the end thereof in contact with the firstnamed pivoted plate, and means on the plate supporting the other end ofthe spring in a plane between the point of attachment of the first namedend thereof to the actuator and the pivot point of the actuator, thearrangement providing that, as the first named pivoted plate is moved onits pivot, the end of the spring supported by said movable end of thefirst named plate is moved to one side of the pivot point of theactuator, the said actuator is turned on its plane occupied by the pivotby the spring to move the said movable contact against the tension ofits pring to break the circuit.

5. A pressure controlled electric switch comprising a frame, a pair ofcontacts of an electric circuit supported in insulated relation by theframe, a movable contact element for making and breaking the circuit, aspring tending to move the said movable contact element tomake thecircuit, means for moving said movable contact to break the circuitcomprising a plate pivoted at one end to the frame, spring means at theopposite movable end of the plate for resisting turning of the plate inone direction on its pivot, pressure actuated means for turning theplate on its pivot against the tension of said spring means, a switchactuator comprising an L-shaped member pivotally supported at one end bythe frame at a point spaced from the movable end of the plate, and withthe opposite free end engaging the plate adjacent its pivot point, aspring attached at one end. to the L-shaped member adjacent the endthereof in contact with the plate, and means at the movable end of theplate supporting the other end of the spring in a plane between thepoint of attachment of the first named end thereof to the L-shapedmember and the pivot point of the plate, the arrangement providing that,as the plate is moved on its pivot, the end of the spring for theL-shaped member supported at said movable end of the plate is moved toone side of the plane occupied by the pivot point of the plate, the saidL-shaped member is turned on its pivot by its spring to move the saidmovable contact against the tension of its spring to break the circuit.and means carried by the plate for varying the tension of the actuatorspring.

STANLEY R. DU BRIE.

